1. Field of the Invention
The present invention relates in general to the implementation of a GPS receiver and in particular to the method and apparatus for implementing a GPS receiver on a single integrated circuit.
2. Description of the Related Art
Almost all modern wireless products use a radio section coupled to a digital section. These two sections are often constructed using dissimilar technologies, to optimize differing constraints for each function. A great deal of effort has been expended in the industry to decrease the size of the implementations. Users of GPS technology often integrate the GPS receivers into other functions, such as cellular handsets, and these users demand as small a size as possible for the GPS function.
A system where the radio section and the processing section are constructed on a common die can be designed to be extremely small, relative to current implementations. The term “common die” means these two functions are constructed together and when used they are not cut apart and mounted separately, but remain together as a single integrated circuit. In the past the technologies used to construct the two functions have made it difficult to realize these two functions as a single integrated circuit on a common substrate, and use that integrated circuit to construct a GPS receiver.
Design techniques have been developed to allow for the possibility of the rf and digital operating on a common substrate, and also allow for these two functions to have the necessary functionality needed to implement a fully functional GPS receiver.
This invention addresses the issues that arise when a digital section is in close physical and electrical proximity to a sensitive radio receiver. When the digital section is operating it can, and usually does, create a great deal of noise that can interfere with the operation of the radio receiver. Standard methods used in the industry to alleviate these issues do not work well enough when the radio section and the digital section are constructed on the same substrate, in an integrated circuit. The standard techniques of spatial separation, and shielding are not practical, and integrated circuit techniques such as isolating the various circuit functions with ground rings or trenches are not effective enough. Other techniques need to be created to allow adequate performance of the GPS receiver. GPS receivers are particularly sensitive receivers, and extra care must be made to allow them to operate without reduced sensitivity.
It can be seen, then, that there is a need in the art for a method of reducing the effects of the coupling of noise from one function in an integrated GPS receiver to another function.